Process of treating hides



UNITED STATES PATENT OFFICE.

CHARLES S. DOLLEY AND ALBERT F. CRANK, OF PHILADELPHIA, PENNSYLVANIA.

PROCESS OF TREATING HIDES, SKINS, OR- LEATHER.

SPECIFICATION forming part of Letters Patent No. 642,519, dated January30, 1900.

Application filed November 9, 1898. Serial No. 695,967. (No specimens.)

To aZZ whom it may concern:

Be it known that We, CHARLES S. DOLLEY and ALBERT F. CRANK, citizens ofthe United States, residing at Philadelphia, in the county ofPhiladelphia and State of Pennsylvania, have invented certain new anduseful Improvements in Processes of Treating Hides, Skins, or Leather;and we do declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

This invention relates to certain new and useful improvements inprocesses for treating hides, skins, and leather; and the objects of theinvention are to provide a process by means of whicha superior leathercan be produced either from raw hides or skins or from such hides orskins as have been previously tawed or from such as have been partly butimperfectly tanned and which do not meet the Various tests which arecommonly employed to determine perfectly-tanned leather and which aretherefore susceptible to improvement.

Certain varieties of skins (as is the case with East India kips andgoatskins, basils, and white leather) are for convenience of shipment orfor other reasons placed upon the market in a tawed or animperfectly-tanned condition. Such skins in many cases do not respondfavorably to the usual tests for perfoot leather, and hence requiresubsequent treatment.

Certain methods of tanning throw upon the market a considerable amountof imperfect leather which is susceptible to improvementas, forinstance, that treated with cutch or terra japonica, dividivi, &c.,which, if properly tanned, would command higher prices.

It is one of the objects of the present invention to take such tawed andpoorly-tanned leather and by proper treatment to convert the same intomore nearly perfect leather, thusgreatly enhancing its value.

The invention has for a further object to fix in the skins or hides suchsubstancesfor example, extractives, coloring-matter, fillers, naturaland artificial tannins, &c.-as may be employed with the purpose offeeding the leather and of providing it with certain desired physicalcharacters, such as plumpness,

weight, color, softness, impermeability to moisture, 850.

Our invention consists, essentially, of two steps, the first of which isconcerned with the introduction into the hide or skin of some materialor materials which will render the skin sensitive to the fixing ortanning agent employed in the second step by overcoming theagglutinatiug action of the interfibrillar ground substance (mucin,coriin, 8m.) and effect a splitting up of the connective-tissuefiber-bundles,with an accompanying swelling and separation of the fibersand fibrils, pr0- ducing thereby a fulling or plumping effect, clearingthe grain and at the same time feeding the leatheri. a, impregnating theskin with materials the presence of which is desirable for theproduction of the physical qualities noted above. This first step hasthe same purpose as that commonlyattained by the employment of old andsour liquors and weak solutions of extractives and which precedes theactual tanning process. The second step of the process consists intreating the hide or skin to the action of formicaldehyd, (01120,) amaterial possessing the property of fixing the connective-tissue fibersand fibrils on the swelled and plumped, tawed, or partiallytannedcondition produced by the first treatment and at the same time of fixingin, upon, or between the fibers and fibrils of the connective-tissuematerials which have been supplied by the first step of the process tocontribute special physical qualities-such as body, color, suppleness,weight, &c.-essential to a solid well-nourished leather. The use of theformicaldehyd in this second step is not a mere aggregation of elementsor materials, as it is in its nature and effects entirely different fromthe materials employed in the first' step and could not be substitutedfor them to produce the effects of the first step, while itpossessesdistinctive and positive characters by which it acts upon both the skinand the materials with which it has been impregnated by the first stepin a manner peculiar to itself, as will be hereinafter more fully setforth.

In carrying out our invention we take ad vantage of the propertypossessed by various tawing and tanning agents such as alum, salt,argol, eggs, fiour,vegetable extractives, gambier, and cutch and theartificial and natural tannins used in making leather, many of whichhave none or only feeble tanning propertiesof causing a swelling up orseparation of the fibers and fibrils of the skin-connective tissue andthe deposition in, upon, and between the same of materials which preventthem from again becoming agglutinated, thereby allowing the interlacingfibers to move readily upon each other and which at the same time addmaterial to the skin, which is of ad vantage in respect to weight, body,color, the, whereby a plump, soft, pliable, tough, and elastic leathermay be produced. Owing to the manifold qualities and varieties ofleather required in the various industries it is impossible for us tospecify any one of the agentssuch as alum, salt, eggs, flour,extractives, reds, gambier, tannins, &c.as being capable of meeting allrequirements, and in the first step of our process we hold ourselvesfree to use any or all materials which will produce the effect oreffects desired-win, the separation and swelling of the fibers andfibrils and the clearing and raising of the grain, together with theplumping, filling, coloring, weighting, and rendering supple the skininshort, the operation preparatory to the subsequent fixing action offormicaldehyd as employed in our second step-an action in some respectsanalogous to that ordinarily secured by means of those tannins which arecapable of rendering gelatin insoluble, but in many respects peculiar toitself.

The ultimate object of the invention in usi ug thematerials designatedin the first step of our process is to secure desirable states andqualities in the hides or skins treated, which may be fixed orsupplemental therein by the action of formicaldehyd subsequently appliedin the second step, as hereinafter described. The following particularcase will serve to illustrate the steps involved in our process.

Commercial sheepor goat skins or hides having been previously preparedfor treatment by softening, unhairing, or other necessary and ordinarysteps, usually referred to as beam-house treatment, are placed in a drumor reel, in which they maybe agitated by the revolving of thereceptacle, by paddles, or by any other suitable means, the particularmethod or mechanism employed constituting no part of the presentinvention. We hold ourselves free to employ any form of receptacle ormethod of agitation whatsoever. Together with the hides or skins in thereceptacle is placed a solution of gambier extract sufficiently dilutedto present the extract to the entire mass of the skins, containing,approximately, four pounds of gambier .to each one hundred pounds of wethides or skins, the exact amount of gambier being based upon the weightof the skins or hides to be treated and also upon their acidity oralkalinity, according to well-known gambier desired, in a'specialreceptacle.

tents agitated-factors which do not concern the principle involved inthe process. When the gambier has struck through or thoroughly permeatedthe skins, (which may be ascertained by cutting into the thickest edgeand examining the exposed interior,) the skins are rinsed in cleanwater; but this Washing or rinsing may, if preferred, be dispensed with,and the second step proceeded withat once, and we do not wish to be heldto washing the skins as a feature essential to our process.

I live wish it clearly understood that the object of the first step ofour process is, as has been previously stated, to bring the skins into adesired physical condition, characterized by such a separation andswelling of "the tissue fibers and fibrils and such plum pness, weight,color, and suppleness as will, when fixed by the chemical action offormicaldehyd, constitute a superior leather of the particular characterdesired. Thus we are able to develop the desired physical characters bymeans of alum, salt, argol, eggs, flour, the tannins, gambier, and othervegetable extracts. In the first step, therefore, it is not so much aquestion of the materials employed, as there is a wide choice in thisrespect, but rather the securing of physical qualities in the skin,which we proceed to supplement, fix, and render permanent by the secondstep. The use of saline and sour liquors serves to swell the tissues andfibers of the skin and to render it more readily affected by the tanningor fixing agent subsequently employed, while the vegetable extractivesor their equivalents add color, weight, &c.

I The second step of our process consists in subjecting the skins orhides to the action of formicaldehyd, preferably in solution, al-

though it may be employed in the state of gas,

either in the same receptacle in which they were given the preliminarytreatment, or, if The amount of the solution employed various somewhat,but is based upon the weight of the skins or hides to be treated, and wehave found in practice that three pounds of commercial forty percent.(40 formicaldeh yd solution to each onehundred pounds of wet hides orskins is sufficient for ordinary sheep or goat skins. The amount ofwater with which the formicaldehyd is diluted is based upon the bulk ofskins, being just sufficient to keep them well wetled and to present theformicaldehyd to the entire mass of the skins, but not so much as toprevent the pounding action of the skins when revolving in the drum. Theskins or hides are subjected to the action of TIO formicaldehyd untilpermeated through and through and until they respond to the usual testsfor good leather. In the particular case which is cited herein as anillustration namely, sheep or goat skins we have found that the timerequired is approximately three hours. The time, however, depends toavery considerable extent, as in the treatment by the first step of ourprocess, upon the number of skins in the receptacle, and the rate andmode of agitation to which they have been subjected. It is advisable tomaintain the bath in the second step at a temperature of not less than80 Fahrenheit and not above 120 Fahrenheit, in order to secure thegreatest efiiciency from the formicaldehyd, which under these conditionshas greater penetratio n and less liability to polymerize than at lowtemperatures. After the skins are found to have been thoroughly fixed bythe formicaldehyd they are washed and are then ready for the usualtreatment employed in finishing.

In case the forinicaldehyd is employed in the state of a gas we preferthe following method: The skins having been brought to the desired stateby the first step, as hereinbefore described, an amount of commercialformicaldehyd (forty per cent.) solution, representing, approximately,three pounds to each one hundred pounds of wet hides or skins to betreated, is placed in a suitable generator, a Variety of which are uponthe market, and

. the gas generated is allowed to pass by suitable connections into thechamber containing the skins. The temperature of this chamber ispreferably maintained at from 100 Fahrenheit to 120 Fahrenheit, and theatmosphere of the chamber should also be kept moist, both of whichconditions are readily secured by the admission from time to time of asmall quantity of warm aqueous vapor by means of a suitable steamconnection. The chamber employed should be a closed one and no largerthan necessary to allow the skins to be fully exposed to the action ofthe gas. If desired, the gas may be admitted to the drum in which thepreliminary treatment took place or into a similar drum and the skinsagitated therein, or the skins may be stretched on suitable frames andinclosed within a stationary chamber, in either case being exposed tothe action of the gas until they respond to the usual tests for goodleathersay for a period of six hours-the time depending, however, on thethickness and character of the skins under treatment.

The market supplies certain tawed or imperfectly-tanned skins and hideswhich have been already subjected to the action of salt and alum, fiour,eggs, vegetable extractives, gambier,cutch,tannins,orother materials andwhich do not constitute high-grade leather, but which are susceptible ofimprovement. The effects produced on these skins are analogous to thoseproduced by the first step of our process, and we find it both possibleand advantageous to take such skins and after softening them in waterproceed to treat them as described in the example cited for treating rawskins, whereby we are able to secure the results of. the first step withless time and material than would be required in treating green or rawhides or skins, and in certain cases where the tawed orimperfectly-tanned skins or hides have the plumpness, color, weight,&c., desired and which we would have secured by means of our first stepwe may proceed at once to the second step of the process, whichconsists, essentially, in the fixation of the natural or addedconstituents of the skin, substantially as described.

\Ve have found bya large number of practical tests that the actualtanning efiect of the natural tannins as introduced into the skin by thefirst step of our process may be greatly hastened and augmented by theemployment of .formicaldehyd in conjunction therewith as accomplished bythe second step of our process. Thus with the pyrogallol tannins, aconsiderable proportion of which possesses little or no tanning power, acompound is formed whereby all the tannin is rendered available, andconsequently a greater action secured from a given amount of-extractamatter of importance in point of economy. Again, we find that by meansof formicaldehydused in conjunction with, but subsequent to, the use ofthose natural (catechol) tannins containing phlobophanes or reds, asintroduced into the hides by the first step of our process, thesesubstances, which in:many instances are insoluble and not directlyavailable for tanning, can be fixed in the leather; and, again, withother (pyrogallol) tannins the deposit of whites or bloom is prevented,the ellagic acid or catechin being in some way altered and in.-dissolubly bound in combination with the skin substance, as are alsocertain extractives (e. g., gambier) by the action of the formicaldehydupon the impregnated collagen of the skin, whereby an occlusion of theintroduced material is brought about, and also by its direct action uponthe catechus themselves, whereby they are rendered insoluble andprecipitated as a filling and coloring material upon and between thefibers and fibrils of the skin-connective tissue, thus effecting what istechnically known as feedthey are when subjected to its action, and wehave found that it is highly advantageous in using formicaldehyd in themanufacture of leather to prepare the skins or hides by some preliminarytreatment, as by our first step, whereby the fibers and fibrils of theconnective tissue are properly separated and swelled or plumped, coloredor filled, as seems desirable in the particular case in hand, when they,together with the other gelatigenous constituents of the skin, may befixed in the particular state desired, by the use of formicaldehyd ashas been previously described, and which constitutes the second step ofour process. Our invention therefore'proposes the application offormicaldehyd to hides and skins, the collagen of which is either not atall or but partially combined into insoluble compounds either, first,from a lack of suitable quality in the agents used in the preliminarytreatment, such agents being, for example, salt, eggs, flour, alum,argol, vegetable extractives, gambier, cutch, and such othertannin-containing materials possessing little or no tanning properties,or, second, from lack of sufficient combination with an agent, such asoak or hemlock tannin, which is potentially capable of saturating thecollagen and forming therewith an insoluble and imputrescible compound,but which in the skins we propose to treat has de facto not fullysaturated the collagen. In other words, We propose to applyformicaldehyd to hides or skins containing a soluble ..collagen compoundor unsaturated collagen. We therefore employ formicaldehyd to fix thecollagen of the skins after the skins have been prepared by suchprocesses as produce the qualities peculiar to ordinary salt and alumtawed skins, chamois-leather, oil -tawed leather, Wash-leather, Knappsleather, &c., or the peculiar leather resulting from the employ-- mentof gambier and similar vegetableextracts or where the fixation of thetissue constituents has been imperfectly accomplished by the ordinarytannin g processes. The skins may be specially prepared, or tawed skins,chamois-leather, &c., .may be taken ready prepared and submitted to thefixing action of formicaldehyd.

Much of the leather commonly regarded as well tanned is open to greatimprovement, and our invention proposes the employment of the ordinaryprocesses of tanning as our first step or the taking of commercialleather already prepared by others and submitting it to the fixing andsupplemental action of formicaldehyd as a second or final step in theproduction of perfectly-tanned leather. Our invention therefore involvesthe use of formicaldehyd subsequent to the use of tawing or tanningmaterials, and inasmuch as these materials give varying degrees ofplumpness, weight, density, and color to hides and skins our inventionnecessarily involves the use of formicaldehyd in conjunction with allmaterials producing these eifects in accordance with our process ashereinbefore described.

(e do not confine ourselves to the use of any one tawing or tanning,plumping, feeding, or coloring material in conjunction withformicaldehyd, as our process is not limited to the production of anyone kind of leather, but is applicable to the production of either lightor heavy leather, white or colored, as desired-in fact, to all varietiesof leather, and its employment as herein described results in a verymaterial saving in time, labor, and materials. I

We desire to have it understood that in the use of the word tanning inthis specification we use the word in its broad or generic sense.

Having thus described our invention, What We claim to be new, and desireto secure by Letters Patent, is-- 1. The process for the production ofleather, which consists in the application of formicaldehyd to hides orskins which have previously been treated with tanning or tawingmaterials to such an extent that only a mechanical or loose chemicalcombination with the collagen has been effected.

2. The process for the production of leather, which consists insubmitting to formicaldehyd, skins which have been tanned as far aspossible by the ordinary tanning agents.

The process for the production of leather, which consists in treatinghides or skins with tanning materials incapable of rendering thegelatigenous constituents of the skins insolu ble, and then submittingthe skins or hides to the action of formicaldehyd.

4. The process of producing leather, which consists in submitting to theaction of formicaldehyd, skins or hides in which the fixation of thegelatigenous constituents has been imperfectly accomplished by theordinary tanning processes. I

5. The process of producing leather, consist-in g in subjecting hides orskins to tanning materials to such an extent that the hides or skins areconverted into completely-tanned leather, the tanning material being ofsucha character that the leather so produced when immersed in waterbecomes hard byreason of a partial breaking up of the compounds betweenthe tanning material and the collagenous matter of the skins, and thensubjecting the leather to formicaldehyd, whereby the leather is renderedwaterproof, the compound of collagen and the tanning material beingrendered incapable of being broken up by water and the leather remainingsoft after soaking in water.

In testimony whereof we affix our signatures in presence of twowitnesses.

CHARLES'S. DOLLEY. ALBERT F. CRANK.

Witnesses:

CHAS. I-I. BANNARD, WALTER T. STOKES.

IIO

